JP5500205B2 - Fuel supply / discharge mechanism of traveling crane - Google Patents

Description

  The present invention relates to a fuel supply / discharge mechanism for a traveling crane.

  2. Description of the Related Art Conventionally, a fuel supply / discharge mechanism that supplies fuel to a plurality of injectors of an engine of a traveling vehicle and collects excess fuel discharged from each injector is known. Patent Document 1 below discloses an example of such a fuel supply / discharge mechanism.

  The fuel supply / discharge mechanism disclosed in Patent Literature 1 performs a pressure accumulation of a main tank that stores fuel, a feed pump that sucks fuel from the main tank and discharges the fuel to the injector side, and a fuel that is discharged from the feed pump, A common rail that distributes and supplies the fuel to each injector and a return pipe that returns excess fuel discharged from each injector to the main tank are provided. The engine is provided with a plurality of cylinders corresponding to each injector, and an intake valve and an exhaust valve are provided for each cylinder. During the operation of the engine, fuel is injected from the injector into the cylinder and air is introduced from the intake valve, a compression process in which the mixed gas of fuel and air introduced into the cylinder is compressed, and the compression A combustion process in which the mixed gas is burned in the cylinder to generate power and an exhaust process in which exhaust gas after combustion is discharged from the cylinder through the exhaust valve are repeatedly performed. More fuel is supplied to the injector than the amount of fuel required to generate the desired power in the engine, and surplus fuel is discharged from the injector, passes through the return pipe, and is collected into the main tank. Yes.

JP 2010-106662 A

  By the way, when the fuel supply / discharge mechanism as described above is applied to a certain type of traveling crane, air enters the injector while the engine is stopped, and then the startability of the engine deteriorates when the engine is restarted. There is a risk of doing. The reason is as follows.

  Among various traveling cranes, there is a traveling crane in which an engine is mounted on an upper swing body. Moreover, since a traveling crane requires a fuel tank with a very large capacity compared to a passenger car or the like, the main tank is enlarged. The upper swing body of a traveling crane is equipped with hoisting members such as booms and masts, winches, and many other components, so space is limited and it is difficult to install a large main tank. is there. Further, if the main tank is installed on the upper swing body, the refueling work must be performed on the upper swing body, which increases the work load. For these reasons, the main tank is often installed on the lower traveling body of the traveling crane. However, in a traveling crane with an engine mounted on the upper swing body, when the main tank is installed on the lower traveling body in this way, the main tank is disposed at a position lower than the engine, and between the engine and the main tank. Since a large height difference is formed in the return pipe, the pressure in the return pipe becomes negative with respect to the pressure in the injector due to the height difference. When the engine is stopped, the intake valve and exhaust valve provided for each cylinder are both closed and open, and the return pipe is inside the injector. If the air pressure is negative, air may enter the injector corresponding to the valve through the intake valve or the exhaust valve that is open. Since each injector is connected to each other through a common rail, when air enters one of the injectors, the air also enters another injector through the common rail. As a result, fuel injection failure occurs in all injectors when the engine is restarted, and engine startability may deteriorate.

  The present invention has been made to solve the above-described problems, and the object thereof is a traveling crane in which a main tank of fuel is provided in a lower swing body and an engine is provided in an upper swing body. This is to prevent deterioration of engine startability.

  As a means for achieving the above object, it is conceivable to provide a check valve in the middle of the return pipe from the injector to the main tank. According to this configuration, when the engine is stopped, the pressure between the check valve and the injector in the return pipe can be maintained at the set pressure of the check valve, and a large level between the engine and the main tank can be maintained. Even if there is a difference, air can be prevented from entering the injector.

  However, if the check valve has been used for a long period of time, impurities in the fuel may enter the check valve and the check valve may be incompletely shut off. In this case, when the engine is stopped, the fuel between the check valve and the injector in the return pipe gradually escapes to the main tank, and the pressure between the check valve and the injector in the return pipe is reduced. It gradually decreases, and air is sucked into the injector from the open exhaust valve or intake valve. For this reason, when the engine is stopped for a long time, the startability of the engine deteriorates as a result. Further, while the engine is operating, the temperature of the fuel is increasing. However, when the engine is stopped, the temperature of the fuel is decreased and the fuel is contracted. This contraction of the fuel also occurs in the return pipe, which causes a negative pressure in the return pipe. This also causes the air to be sucked into the injector, and the engine startability deteriorates.

  Therefore, in order to solve this problem, the present inventor has invented a fuel supply / discharge mechanism for a traveling crane as follows. A fuel supply / discharge mechanism according to the present invention includes a lower traveling body, an upper revolving body mounted on the lower traveling body so as to be rotatable, an engine provided in the upper revolving body, and the lower traveling body. A main tank for storing fuel to be supplied to the engine, the engine compressing and burning the fuel therein, and a plurality of injectors for supplying the fuel into each cylinder A fuel supply / discharge mechanism for supplying and discharging fuel to and from the engine, a fuel pump for sucking and discharging fuel from the main tank, the fuel pump, and the plurality of injectors And a common rail connected to each of the injectors and supplying the fuel discharged from the fuel pump to the injectors, and the plurality of injectors Connecting the injector and the main tank between the main tank and the main tank, a return pipe for returning the excess fuel discharged from each injector to the main tank, and a sub tank provided in the return pipe; The return pipe has a first return pipe connecting the injector and the sub tank, and a second return pipe connecting the sub tank and the main tank and provided with a check valve. Is filled with fuel up to a position higher than the end of the first return pipe on the sub-tank side, and an air layer having a pressure higher than atmospheric pressure is provided above the filled fuel. ).

  In the fuel supply / discharge mechanism of this traveling crane, a subtank is provided in the return pipe, and the subtank is filled with fuel up to a position higher than the end on the subtank side of the first return pipe connecting the injector and the subtank. Since an air layer higher than atmospheric pressure is provided on the upper side of the fuel in the inside, impurities enter the check valve provided in the second return pipe, and the shut-off function of the check valve becomes incomplete, and the engine stops. Even if the pressure in the second return pipe decreases, the fuel pressure in the first return pipe can be maintained by the pressure of the air layer in the sub tank. For this reason, it can prevent that the pressure in a 1st return piping turns into a negative pressure with respect to atmospheric pressure. As a result, even if the intake valve attached to the injector to which the first return pipe is connected is in an open state, it is possible to prevent air from being sucked into the injector, via the injector and the common rail. Intrusion of air into other connected injectors can also be prevented. Therefore, according to the fuel supply / discharge mechanism of the traveling crane, it is possible to prevent the startability of the engine from being deteriorated even after the engine has been stopped for a long time. Further, in this configuration, even if the temperature of the fuel in the first return pipe decreases due to the engine stop and the fuel contracts, the pressure drop in the first return pipe due to the contraction of the fuel is reduced in the sub tank. It can be compensated by the pressure of the air layer. For this reason, the pressure drop in the first return pipe due to the temperature drop of the fuel can be suppressed, and the intake of air into the injector due to the factor can be prevented.

  In the fuel supply / discharge mechanism of the traveling crane, the end portion on the sub tank side of the second return pipe is disposed at a position higher than the end portion on the sub tank side of the first return pipe in the sub tank. (Claim 2).

  According to this configuration, even if the leakage of fuel to the main tank side through the check valve proceeds and the fuel in the sub tank decreases while the engine is stopped, the oil level of the fuel in the sub tank is increased. The position does not fall below the height position of the end of the second return pipe in the sub tank. For this reason, it can prevent that the edge part of the 1st return piping arrange | positioned in the position lower than the edge part of 2nd return piping in a subtank is exposed in the air layer above fuel, and 1st return Air can be prevented from entering the injector through the pipe.

  In the fuel supply / discharge mechanism of the traveling crane, it is preferable that the sub tank is disposed at a position higher than the injector.

  According to this configuration, since the pressure due to the difference in height between the sub tank and the injector is added to the pressure applied to the fuel in the first return pipe from the air layer in the sub tank, the air to the injector when the engine is stopped Can be more effectively prevented.

  In the fuel supply / discharge mechanism of the traveling crane, a resistance imparting unit is provided in the sub tank for applying a flow resistance to the fuel when the fuel in the sub tank is shaken to suppress the fuel shake. (Claim 4).

  According to this configuration, even when vibration or the like is given to the sub tank and the fuel in the sub tank is shaken, the resistance applying portion can suppress the fuel shake, so the end portion on the sub tank side of the first return pipe is Exposure to the air layer above the fuel can be suppressed. Therefore, in this configuration, when the fuel in the sub tank shakes, the air in the sub tank can be prevented from entering the injector through the first return pipe.

  In this case, the resistance applying portion is a partition wall horizontally disposed in a position higher than the end portion on the sub tank side of the first return pipe and the end portion on the sub tank side of the second return pipe in the sub tank. The partition wall may be formed with a through hole for allowing the fuel to flow therethrough (Claim 5).

  According to this configuration, when the fuel in the sub-tank shakes, air is prevented from entering the first return pipe by the partition wall, and when the internal pressure of the first return pipe and the second return pipe decreases, the partition wall The fuel in the sub-tank can smoothly flow to the first return pipe and the second return pipe through the formed through hole.

  As described above, according to the present invention, in the traveling crane in which the main tank of fuel is provided in the lower turning body and the engine is provided in the upper turning body, even after the engine is stopped for a long time, Deterioration of engine startability can be prevented.

1 is a schematic side view of a traveling crane to which a fuel supply / discharge mechanism according to an embodiment of the present invention is applied. 1 is a schematic circuit diagram of a fuel supply / discharge mechanism according to an embodiment of the present invention. It is a longitudinal cross-sectional view of the sub tank which comprises a fuel supply / discharge mechanism. It is sectional drawing of the sub tank along the IV-IV line in FIG. It is sectional drawing of the subtank along the VV line in FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  The fuel supply / discharge mechanism according to the embodiment of the present invention is provided in a traveling crane, supplies fuel to the engine 106, and collects excess fuel discharged from the injector of the engine 106.

  In this embodiment, the traveling crane is a so-called wheel crane, as shown in FIG. 1, and an upper swing mounted on the lower traveling body 102 so as to be rotatable about the vertical axis on the lower traveling body 102. And a body 104.

  The lower traveling body 102 is provided with a main tank 108 that stores fuel to be supplied to the engine 106. The main tank 108 is large in order to ensure a large capacity, and has a capacity of several hundred liters. The lower traveling body 102 is provided with an unillustrated traveling drive mechanism for rotating the wheel 102 a to travel the lower traveling body 102.

  The upper turning body 104 is provided such that the lower surface thereof is located at a height of about 2 m from the ground. The upper swing body 104 includes an engine 106, a boom 107, a hoisting cylinder 110 for hoisting the boom 107, an unillustrated telescopic cylinder for extending and lowering the boom 107, and a hook 112 suspended from the tip of the boom 107. An unillustrated hydraulic winch for raising and lowering, an unillustrated turning hydraulic drive mechanism for turning the upper turning body 104, an unillustrated hydraulic pump, and the like are provided. In the traveling crane of this embodiment, a hydraulic pump (not shown) is driven by the power output from the engine 106, and the traveling and turning of the lower traveling body 102 by the traveling drive mechanism is performed using the hydraulic pressure supplied from the hydraulic pump. The upper revolving body 104 is turned by the hydraulic drive mechanism, the boom 106 is raised and lowered by the hoisting cylinder 110, the boom 106 is expanded and contracted by the telescopic cylinder, and the hook 112 is lifted and lowered by the hydraulic winch. Further, in the present embodiment, the engine 106 is provided on the upper swing body 104 and the main tank 108 is provided on the lower traveling body 102, so that the engine 106 is disposed at a position higher than the main tank 108. A large height difference is formed between the engine 106 and the main tank 108.

  The engine 106 includes a plurality of cylinders 106a, a plurality of injectors 106b, a plurality of intake valves 106c, and a plurality of exhaust valves 106d (see FIG. 2). In FIG. 2, only one set of cylinder 106a, injector 106b, intake valve 106c and exhaust valve 106d is shown, and the other cylinders 106a, injector 106b, intake valve 106c and exhaust valve 106d are not shown.

  Each cylinder 106a compresses and burns the mixed gas of fuel and air inside. Specifically, a piston 106e is accommodated in each cylinder 106a, and the piston 106e moves upward in the cylinder 106a to compress the mixed gas of fuel and air.

  The injector 106b is provided at the top of each cylinder 106a. The injector 106b supplies (injects) fuel into the cylinder 106a. Note that the height difference between the injector 106b and the main tank 108 is, for example, 1.5 m or more. The injector 106b includes a nozzle 106f and an injection valve 106g provided in the nozzle 106f. When the injection valve 106g is opened, fuel is injected into the cylinder 106a from the tip of the nozzle 106f. It has become.

  The intake valve 106c and the exhaust valve 106d are provided in the upper part of each cylinder 106a. An intake passage 106h and an exhaust passage 106i are connected to the cylinder 106a, an intake valve 106c is provided at a connection portion of the intake passage 106h with respect to a space in the cylinder 106a, and an exhaust valve 106d is a space in the cylinder 106a. Is provided at the connection portion of the exhaust passage 106i.

  The intake valve 106c is movable between an open position where the intake passage 106h and the space in the cylinder 106a are communicated and a closed position where communication between the intake passage 106h and the space within the cylinder 106a is blocked. The intake passage 106h is open to the atmosphere, and when the intake valve 106c moves to the open position, the intake passage 106h communicates with the space in the cylinder 106a, and air can be taken into the cylinder 106a through the intake passage 106h. Become.

  The exhaust valve 106d is movable between an open position where the exhaust path 106i communicates with the space inside the cylinder 106a and a closed position where the communication between the exhaust path 106i and the space inside the cylinder 106a is blocked. The exhaust path 106i is open to the atmosphere like the intake path 106h. When the exhaust valve 106d moves to the open position, the exhaust path 106i and the space in the cylinder 106a communicate with each other, and the exhaust path 106i from the cylinder 106a. The exhaust gas can be discharged through.

  In the engine 106 having the above-described configuration, power is generated by repeatedly performing an intake process, a compression process, a combustion process, and an exhaust process in order. Specifically, in the intake process, the intake valve 106c moves to the open position, and air is taken into the cylinder 106b from the intake passage 106h as the piston 106e moves downward. Next, in the compression process, the piston 106e moves upward to compress the air in the cylinder 106b, and the injection valve 106g of the injector 106b is opened just before the compression is completed, so that the injector 106b enters the cylinder 106b. Fuel is injected. Thereafter, in the combustion stroke, the compressed air / fuel mixed gas is burned to generate an explosive force, which pushes the piston 106 e downward to generate power. Thereafter, in the exhaust process, the exhaust valve 106d moves to the open position, and the piston 106e moves upward, whereby exhaust gas is discharged from the cylinder 106b to the exhaust passage 106i. In such an engine 106, when the engine 106 is stopped, the injection valve 106g of the injector 106b is in an open state and the intake valve 106c is disposed in the open position, and the intake passage 106h, the space in the cylinder 106b, the inside of the injector 106b, There are cases where there is a communication. In this case, if the pressure in the first return pipe 14a connected to the injector 106b becomes a negative pressure with respect to the pressure in the injector 106b (atmospheric pressure), air is introduced into the cylinder 106b from the intake passage 106h. I will be sucked.

  The fuel supply / discharge mechanism according to the present embodiment is configured to prevent such suction of air into the injector 106b. Specifically, the fuel supply / discharge mechanism according to this embodiment includes a supply pipe 2, a fuel supply pump 4, a filter 8, a common rail 10, a supply side check valve 12, a return pipe 14, and a return side check valve. 16 and a sub tank 18 are provided.

  The supply pipe 2 is a pipe that connects the main tank 108 and the plurality of injectors 106 b of the engine 106. The supply pipe 2 includes a first supply pipe 2a that connects the main tank 108 and the fuel supply pump 4, a second supply pipe 2b that connects the fuel supply pump 4 and the common rail 10, and the common rail 10 and a plurality of injectors 106b. It is comprised by the some 3rd supply piping 2c to connect.

  The first supply pipe 2a is provided with a filter 8 and a supply side check valve 12. The filter 8 is for removing foreign matters contained in the fuel, and the supply side check valve 12 is for preventing the back flow of fuel from the fuel supply pump 4 to the main tank 108 side.

  The fuel supply pump 4 sucks fuel from the main tank 108 through the first supply pipe 2a. As a result, the fuel from which foreign matter has been removed by the filter 8 is introduced into the fuel supply pump 4, and the fuel supply pump 4 increases the pressure of the sucked fuel and sends it to the common rail 10 through the second supply pipe 2b. The fuel supply pump 4 is included in the concept of the “fuel pump” of the present invention.

  The common rail 10 temporarily stores fuel sent from the fuel injection pump 6, and distributes and supplies the fuel to the injectors 106b. The common rail 10 accumulates the pressure of fuel sent from the fuel injection pump 6 in a high pressure state, and distributes the accumulated fuel to the injectors 106b through the third supply pipes 2c.

  The return pipe 14 is a pipe for connecting the injectors 106 b and the main tank 108 between the plurality of injectors 106 b and the main tank 108, and returning surplus fuel discharged from each injector 106 b to the main tank 108. . A sub tank 18 is provided in the return pipe 14. The return pipe 14 includes a first return pipe 14 a that connects each injector 106 b and the sub tank 18, and a second return pipe 14 b that connects the sub tank 18 and the main tank 108. The first return pipe 14 a is configured by a plurality of branch pipes 14 c connected to the respective injectors 106 b and a common connection pipe 14 d connected to the end of these branch pipes 14 c, and this connection pipe 14 d is connected to the sub tank 18. Has been. Specifically, each branch pipe 14c is connected to the injector 106b so as to derive surplus fuel discharged (overflowed) from the corresponding injector 106b. Further, the connecting pipe 14d is connected to the bottom of the sub tank 18 so that the first return pipe 14a communicates with the space in the sub tank 18.

  The end of the second return pipe 14b on the sub tank 18 side is connected to the bottom of the sub tank 18, whereby the second return pipe 14b communicates with the space in the sub tank 18. The end of the second return pipe 14b on the sub tank 18 side is disposed in a position higher than the end of the connection pipe 14d of the first return pipe 14a on the sub tank 18 side.

  The return side check valve 16 is provided in the second return pipe 14b. The return-side check valve 16 maintains the pressure at the portion on the sub tank 18 side with respect to the return-side check valve 16 in the second return pipe 14b at a predetermined set pressure or higher, and the pressure at that portion is the set pressure. If it is above, the distribution | circulation of the fuel from the sub tank 18 side to the main tank 108 side is permitted. The return side check valve 16 is included in the concept of the “check valve” of the present invention.

  The sub tank 18 is a sealed tank that temporarily stores excess fuel discharged from each injector 106b. The sub tank 18 has a smaller capacity and a smaller size than the main tank 108. The sub tank 18 is filled with fuel in the lower part, and an air layer having a pressure higher than atmospheric pressure is provided above the fuel. The sub tank 18 is formed in a substantially cylindrical shape whose both ends in the axial direction are closed, and is provided on the upper swing body 104 so that the axial direction coincides with the vertical direction. Further, the sub tank 18 is disposed at a position higher than all the injectors 106b. As shown in FIG. 3, the sub tank 18 includes a bottom wall 18 a that constitutes the lower surface thereof, and a top wall 18 b that constitutes the upper surface thereof. A first connection hole 18c for connection of the first return pipe 14a and a second connection hole 18d for connection of the second return pipe 14b pass through the bottom wall 18a in the bottom wall 18a of the sub tank 18. Is formed. The end of the connection pipe 14d of the first return pipe 14a is fixed to the bottom wall 18a in a state of being inserted into the first connection hole 18c. The end of the second return pipe 14b is inserted through the second connection hole 18d and protrudes upward from the bottom surface in the sub tank 18 (the top surface of the bottom wall 18a). The sub tank 18 is filled with fuel up to a position higher than the end of the second return pipe 14b on the sub tank 18 side. Therefore, the sub tank 18 is filled with fuel up to a position higher than the end of the connection pipe 14d of the first return pipe 14a on the sub tank 18 side.

  A drain opening 18 e is provided in the bottom wall 18 a of the sub tank 18. The drain opening 18e is sealed with a cap (not shown) when fuel is introduced into the sub tank 18. On the other hand, the drain opening 18e is opened when it is desired to discharge the fuel in the sub tank 18, and the drain opening 18e passes through the drain opening 18e. The fuel is discharged. The top wall 18b of the sub tank 18 is provided with an air vent opening 18f. The air vent opening 18f is normally sealed by a cap (not shown), and is opened when the pressure of the air layer in the sub tank 18 is lowered, and air is vented through the air vent opening 18f.

  Further, in the sub tank 18, there is provided a resistance applying portion 19 for applying a flow resistance to the fuel when the fuel in the sub tank 18 is shaken to suppress the fuel shake. The resistance applying portion 19 includes an upper partition wall 19a and a lower partition wall 19b that are installed so as to give flow resistance to the fuel swaying in the sub tank 18. The upper partition wall 19a and the lower partition wall 19b are provided in a position above the end of the second return pipe 14b in the sub tank 18. The upper partition wall 19 a and the lower partition wall 19 b are each formed in a substantially disk shape corresponding to the shape of the inner peripheral surface of the sub tank 18, and are disposed so as to be perpendicular to the axial direction of the sub tank 18. That is, the upper partition wall 19a and the lower partition wall 19b are disposed horizontally and in parallel with each other. Further, the upper partition wall 19a and the lower partition wall 19b are arranged with a space therebetween in the axial direction (vertical direction) of the sub tank 18. The upper partition wall 19 a and the lower partition wall 19 b are attached to the sub tank 18 by welding their peripheral edges to the inner peripheral surface of the sub tank 18.

  As shown in FIG. 4, a plurality of peripheral through holes 19c are formed in the peripheral portion of the upper partition wall 19a at intervals in the circumferential direction. A central through hole 19d is formed at the center of the upper partition wall 19a. In addition, a plurality of peripheral through holes 19e are formed at the same position as the plurality of peripheral through holes 19c of the upper partition 19a in the peripheral portion of the lower partition 19b. In addition, inner through-holes 19f are formed in two regions that are symmetrical to each other in the radial direction with respect to the center of the lower partition wall 19b in the inner region with respect to the periphery of the lower partition wall 19b. The peripheral through hole 19c, the central through hole 19d, the peripheral through hole 19e, and the inner through hole 19f are included in the concept of the “through hole” in the present invention. In the sub tank 18, the fuel passes through a plurality of peripheral through holes 19c and a central through hole 19d formed in the upper partition wall 19a, and a plurality of peripheral through holes 19e and an inner through hole 19f formed in the lower partition wall 19b. It can distribute | circulate between the upper and lower sides of both the partition walls 19a and 19b. Even if the fuel in the sub-tank 18 shakes, the flow resistance is given to the fuel passing through the small through holes of the upper partition wall 19a and the lower partition wall 19b, so that the fuel swing is suppressed and the first return pipe 14a is connected. The end of the pipe 14d and the end of the second return pipe 14b are not exposed to the air layer.

  When the sub tank 18 is filled with fuel, first, the air vent opening 18f and the drain opening 18e are closed. In this state, the engine 106 is started and excess fuel is discharged from each injector 106b. Excess fuel is introduced into the sub tank 18 through the first return pipe 14a. As a result, the oil level of the fuel in the sub tank 18 rises, and accordingly, the air layer above the fuel in the sub tank 18 is compressed and the pressure of the air layer rises. The amount of fuel in the sub-tank 18, that is, the height position of the fuel level in the sub-tank 18 changes according to the rotational speed of the engine 106. Specifically, the amount of fuel in the sub tank 18 increases as the rotational speed of the engine 106 increases, and the oil level of the fuel increases. The pressure of the air layer above the fuel changes according to the height of the oil level of the fuel. As a result, the pressure of the air layer above the fuel depends on the increase / decrease in the rotational speed of the engine 106. Increase or decrease. Further, the pressure of the air layer is maintained at a pressure equal to the set pressure of the return side check valve 16 while the engine 106 is stopped, and the set pressure of the return side check valve 16 and the return pipe 14 while the engine 106 is operating. The pressure is equal to the total pressure loss. Specifically, when the engine 106 is stopped, the air layer pressure is about 150 kPa, and when the engine 106 is operating at a low speed, the air layer pressure is about 180 kPa, and the engine 106 is high. When operating at the rotational speed, the pressure in the air layer is about 200 kPa. Therefore, the pressure of the air layer in the sub tank 18 is maintained at a pressure higher than the atmospheric pressure regardless of the operating state (rotation speed) of the engine 106. When the increase in the oil level accompanying the introduction of fuel into the sub tank 18 during the operation of the engine 106 becomes equal to the pressure corresponding to the sum of the set pressure of the return side check valve 16 and the pressure loss of the return pipe 14. The amount of fuel in the sub tank 18 becomes constant.

  In the present embodiment, the fuel is filled in the sub tank 18 up to a position higher than the end of the first return pipe 14a connecting the injector 106b and the sub tank 18 on the sub tank 18 side, and the fuel in the sub tank 18 is largely above the fuel. Since an air layer having a pressure higher than the atmospheric pressure is provided, impurities in the fuel enter the return side check valve 16 provided in the second return pipe 14b, and the shut-off function of the return side check valve 16 becomes incomplete. Even if the pressure in the second return pipe 14b decreases while the engine 106 is stopped, the pressure in the first return pipe 14a can be maintained at a pressure higher than the atmospheric pressure by the pressure of the air layer in the sub tank 18. . For this reason, it can prevent that the pressure in the 1st return piping 14a turns into a negative pressure with respect to atmospheric pressure. For this reason, while the engine 106 is stopped, the injection valve 106g of the injector 106b to which the first return pipe 14a is connected is open, and the intake valve 106c attached to the injector 106b is disposed at the open position. In addition, air can be prevented from being sucked into the injector 106b through the intake passage 106h, and air sucked into the injector 106b can be prevented from entering the other injector 106b through the third supply pipe 2c and the common rail 10. can do. Therefore, in this embodiment, deterioration of the startability of the engine 106 can be prevented even after the engine 106 has been stopped for a long time.

  In the present embodiment, even if the temperature of the fuel in the first return pipe 14a decreases due to the stop of the engine 106 and the fuel contracts, the pressure in the first return pipe 14a due to the contraction of the fuel. The decrease can be compensated by the pressure of the air layer in the sub tank 18. For this reason, the pressure drop in the 1st return piping 14a by the temperature fall of fuel can be suppressed, and the suction of the air to the injector 106b by the said factor can be prevented.

  Further, in the present embodiment, the end portion of the second return pipe 14b on the sub tank 18 side is disposed at a higher position in the sub tank 18 than the end portion of the first return pipe 14a on the sub tank 18 side. During the stop of 106, the fuel leakage to the main tank 108 side through the return side check valve 16 proceeds, and the fuel in the sub tank 18 flows out to the main tank 108 side through the second return pipe 14b and decreases. However, the height position of the oil level of the fuel in the sub tank 18 does not fall below the height position of the end of the second return pipe 14b in the sub tank 18. For this reason, the end of the connection pipe 14d of the first return pipe 14a disposed at a position lower than the end of the second return pipe 14b in the sub tank 18 is prevented from being exposed in the air layer above the fuel. It is possible to prevent air from entering the injectors 106b through the first return pipe 14a.

  In the present embodiment, since the sub tank 18 is arranged at a position higher than all the injectors 106b of the engine 106, the pressure applied to the fuel in the first return pipe 14a from the air layer in the sub tank 18 is increased. The pressure resulting from the difference in height between the sub tank 18 and the injector 106b is applied. Therefore, it is possible to more effectively prevent air from entering each injector 106b while the engine 106 is stopped.

  Further, in the present embodiment, the sub tank 18 is provided with a resistance applying portion 18g for giving a flow resistance to the fuel when the fuel in the sub tank 18 sways to suppress the fuel sway. Even when vibration or the like is given to the sub tank 18 and the fuel in the sub tank 18 shakes, the end of the connection pipe 14d of the first return pipe 14a on the sub tank 18 side is exposed in the air layer above the fuel. Can be suppressed. For this reason, in this embodiment, when the fuel in the subtank 18 shakes, it can suppress that the air in the subtank 18 enters into each injector 106b through the 1st return piping 14a.

  In the present embodiment, the resistance applying portion 18g is positioned higher in the sub tank 18 than the end on the sub tank 18 side of the connection pipe 14d of the first return pipe 14a and the end on the sub tank 18 side of the second return pipe 14b. The partition walls 19a and 19b are formed with through holes 19c, 19d, 19e, and 19f through which fuel is circulated. When the internal pressures of the first return pipe 14a and the second return pipe 14b decrease while the air is prevented from entering into the first return pipe 14a by the partition walls 19a and 19b when the fuel of the fuel is shaken, The fuel in the sub tank 18 is smoothly returned to the first return through the through holes 19c, 19d, 19e, 19f formed in the partition walls 19a, 19b. It can flow to 14a and the second return pipe 14b.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes meanings equivalent to the scope of claims for patent and all modifications within the scope.

  For example, the fuel supply / discharge mechanism according to the present invention can be applied to a type of traveling crane other than a wheel crane. For example, the fuel supply / discharge mechanism may be applied to a crawler crane.

  Moreover, the end part on the sub tank side of the second return pipe may be arranged at a height position equal to or lower than the height position of the end part on the sub tank side of the connection pipe of the first return pipe in the sub tank.

  Moreover, the sub tank may be arrange | positioned in the height position below the height position of the injector of an engine.

  In addition, the resistance applying portion is not necessarily provided in the sub tank. Moreover, even if the resistance imparting portion is provided in the sub tank, the resistance imparting portion is not limited to the one composed of the upper partition and the lower partition in the above-described form. For example, the resistance applying portion may be configured by one partition or three or more partitions. Further, the resistance applying portion may be configured by a partition extending in the axial direction (vertical direction) of the sub tank. Further, the resistance applying portion may be configured by a plurality of partition walls that are not completely overlapped with each other but are displaced.

4 Fuel supply pump (fuel pump)
DESCRIPTION OF SYMBOLS 10 Common rail 14 Return piping 14a 1st return piping 14b 2nd return piping 18 Sub tank 19 Resistance provision part 19a Upper partition (partition wall)
19b Lower partition wall (partition wall)
19c Peripheral through hole (through hole)
19d Center through hole (through hole)
19e Peripheral through hole (through hole)
19f Inner through hole (through hole)
102 Lower traveling body 104 Upper swing body 106 Engine 106a Cylinder 106b Injector 108 Main tank

Claims (5)

A lower traveling body, an upper revolving body mounted on the lower traveling body so as to be turnable, an engine provided in the upper revolving body, and provided in the lower traveling body for supplying to the engine The engine is provided in a traveling crane having a plurality of cylinders that compress and burn the fuel therein, and a plurality of injectors that supply the fuel into each cylinder, A fuel supply / discharge mechanism for supplying and discharging fuel to and from the engine,
A fuel pump for sucking and discharging fuel from the main tank;
A common rail connected between the fuel pump and the plurality of injectors, and distributing and supplying the fuel discharged from the fuel pump to the injectors;
A return pipe for connecting the injectors and the main tank between the plurality of injectors and the main tank, and returning surplus fuel discharged from the injectors to the main tank;
A sub tank provided in the return pipe,
The return pipe has a first return pipe that connects the injector and the sub tank, a second return pipe that connects the sub tank and the main tank, and is provided with a check valve.
In the sub tank, fuel is filled up to a position higher than the end of the first return pipe on the sub tank side, and an air layer having a pressure higher than atmospheric pressure is provided above the filled fuel. Fuel supply / discharge mechanism for traveling crane.   2. The traveling crane according to claim 1, wherein an end portion of the second return pipe on the sub-tank side is disposed in a position higher than an end portion of the first return pipe on the sub-tank side. Fuel supply / discharge mechanism.   The fuel supply / discharge mechanism of the traveling crane according to claim 1, wherein the sub tank is disposed at a position higher than the injector.   The resistance application part for giving the flow resistance to the fuel when the fuel in the said sub tank shakes and suppressing the fluctuation of the said fuel is provided in the said sub tank. The fuel supply / discharge mechanism of the traveling crane according to claim 1.   The resistance applying portion is a partition wall disposed horizontally at a position higher than the end portion on the sub tank side of the first return pipe and the end portion on the sub tank side of the second return pipe in the sub tank, The fuel supply / discharge mechanism for a traveling crane according to claim 4, wherein the partition wall is formed with a through hole for allowing fuel to flow therethrough.

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